Dial type wafer printed circuit switch

ABSTRACT

Ten fixed contacts are arranged in an annular pattern; these members define &#39;&#39;&#39;&#39;tens&#39;&#39;&#39;&#39; contacts. Ten fixed &#39;&#39;&#39;&#39;units&#39;&#39;&#39;&#39; contacts are arranged to lie on an imaginary circle concentric with said annular pattern. A movable contact wiper is arranged for one-ata-time engagement with the &#39;&#39;&#39;&#39;tens&#39;&#39;&#39;&#39; contacts. A member with ten radially extending contact fingers is mounted for rotation and is arranged such that only one of such fingers contacts only one of the &#39;&#39;&#39;&#39;units&#39;&#39;&#39;&#39; contacts at any one time. The contact wiper is mounted for rotation with the contact fingers; during a complete revolution of these two members one hundred switching operations are achieved.

United States Patent [1 1 Szymber Apr. 2, 1974 [54] DIAL TYPE WAFERPRINTED CIRCUIT 3,440,640 4/1969 Droniou 200 11 D x SWITCH 3,531,6039/1970 Ashman 200/11 D [75] lnventor: Oleg Szymber, Elk Grove, 111.Primary Examiner james R Scott [73] Assignee: GAF Corporation, New York,NY. Attorney, g or FirmWalter Kehm; Samson I L n 22 Filed: June 30, 1970[211 App]. No.: 51,169 [57] ABSTRACT Related [1.5. Application Data [63]Continuation-impart of Ser. No. 834,040, Jan. 17,

1969, Pat. No. 3,733,122.

[52] US. Cl. 200/11 DA [51] Int. Cl. H0lh 19/58, HOlh 21/78 [58] Fieldof Search 200/11 D, 11; 317/101 B [56] References Cited UNITED STATESPATENTS 2,896,033 7/1959 Hartz 200/11 D 2,949,522 8/1960 Glueckstein etal." 200/11 D X 3,043,593 7/1962 Koci 200/11 D X 3,152,228 10/1964Broadhead, Jr 200/11 D Ten fixed contacts are arranged in an annularpattern; these members define tens contacts. Ten fixed units contactsare arranged to lie on an imaginary circle concentric with said annularpattern. A movable contact wiper is arranged for one-at-a-timeengagement with the tens contacts. A member with ten radially extendingcontact fingers is mounted for rotation and is arranged such that onlyone of such fingers contacts only one of the units contacts at any onetime. The contact wiper is mounted for rotation with the contactfingers; during a complete revolution of these two members one hundredswitching operations are achieved.

15 Claims, 6 Drawing Figures DIAL TYPE WAFER PRINTED CIRCUIT SWITCHOBJECTS OF THE INVENTION Another object of the present invention is theprovision of a new and improved switching device of the type describedwhich alternately provides for first and second total numbers ofswitching sequences for one complete revolution of certain movablecontacts with respect to the associated fixed contacts.

These and other objects and advantages of the invention will becomeapparent from the following specification disclosing a preferredembodiment shown in the accompanying drawings. I

DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of oneembodiment of the present invention shown in the form of remote input orcontrol console for a random selection slide projector;

FIG. 2 is an exploded isometric view of the contact members containedwithin the control'console of FIG.

FIG. 3 is a top plan view of such contacts;

' FIG. 4 is a bottom plan view of the upper housing member of thecontrol console showing primarily an indicia bearing disk;

FIG. 5 is a schematic of an electric circuit with which the presentinvention may be associated; and

FIG. 6 is a top plan view of a switching device constituting anotherembodiment of the present invention which may be' used in the slideprojector controlled by the remote console shown in FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring primarily to FIG. 1, theremote input or control console, generally designated 10, includes anupper housing or shell 11 suitably secured to a lower housing piece orbase plate 12. A knurled control knob 13 is rotatably supported in anaperture in the shell 1 1, such knob being mounted to a hub member 14,as by means of a fastener 15. It will be understood that rotation of theknob 13 imparts corresponding rotation to the hub 14.

The hub 14 mounts an indicia bearing disk 16 by means of a plurality ofsmall fasteners 17. This disk carries peripherally arranged indicia inthe form of numerals from 1 to 100 in the embodiment shown for purposesof illustration, a segmental portion of such indicia being visiblethrough a window 18 formed in the shell 11. A mark 19 is formed on theshell 11 adjacent one margin of the window 18 to establish a referenceline for the indicia on the disk 16. In other words, the

knob 13 is rotated as appropriate to position the selected number on themark 19.

To facilitate positioning of selected numbers on the disk 16 inalignment with the reference mark 19, the disk 16 includes one hundredperipheral indexing teeth 16a engageable by a spring biased detentbutton 20. It will be understood that this indexing mechanism permitsthe disk 16, and consequently the hub 14, to come to rest only when oneof the numbers on such disk is in disk 16 in alignment with thealignment with the reference mark l9.

The console 10 mounts an actuate button 22, a forward button 23 and areverse button 24. The actuate button 22 is biased in an up position.When such button is depressed, the same engages a spring contact strip25 and thereby forces the latter into engagement with a contact button(not shown), the latter as well as the spring strip 25 being mounted onan insulating board 26 whichmay be formed of a phenolic material orother suitable dielectric material. The spring strip 25 is biased out ofengagement with the associated fixed contact, the distal end of theformer being restrained by a clip 27 mounted on the board 26. It will beunderstood that the contact 25 and its associated fixed contact definean actuate switch for the random selection circuit to be referred tohereinbelow.

Referring to FIG. 4, the forward indexing button 23 includes afrusto-conical camming formation 23a engageable with a complementarysurface on a forward indexing member 28. The member 28 has a recess 28arockably and slidably receiving a pin 29, the latter being fixedlysupported from the underside of the shell 11. This indexing memberincludes a pawl formation 28b engageable with the teeth 16a on the disk16. A wire Spring 31 is supported by a pin 32, which pin is mounted fromthe shell 11. This wire has opposite ends 31a, 31b respectively engagingthe indexing member 28 and a side wall of the shell 11 for urging themember 28 to a position wherein the pawl 28b is out of engagement withthe teeth 16a. When the button 23 is depressed, the member 28 is cammedagainst the force of the spring wire so as to bring the pawl 28b intoengagement with the teeth 16a and step the disk 16 in a for warddirection by an amount so as to bring the successive number on the disk16 into alignment with the reference mark 19.

Similarly, the reverse button 24 includes a frustoconical formation 24afor camming engagement with a complementary surface on a reverseindexing member 33, the latter having a recess 33a receiving a pin 34.The member 33 includes an integral pawl 33b for engagement with theteeth 160. A spring 35 mounted on a pin 36 has opposite ends 35a and 35burging the member 33 to the position shown in FIG. 4. It will beunderstood that when the reverse button 24 is depressed, the pawl 33bcomes into engagement with the teeth 16a for rotating the disk 16 in areverse direction by an amount for positioning the preceding number onthe disk 16 into alignment with the reference mark 19.

At this time it should be mentioned that the remote console or unit 10embodying the present invention may be connected with a random selectionslide projector by a suitable cable, which slide projector (not shown)may embody the random selection circuit disor the immediately precedingslide, such slides may be selected either by manipulation of the knob 13or by actuation of the buttons 23, 24. Other selections may be achievedby manipulation of the knob 13 or by repeated actuation of the buttons23, 24 as desired.

Turning now to FIGS. 2 and 3, the board 26 mounts an annular contactplate 38. Ten arcuate contacts 40 through 49 are mounted around theperiphery of the plate 38 in spaced relation with the latter therebydefining an annular pattern. These contacts may be characterized as tenscontacts. The contacts 40 through 49 have respective, integral, radiallyextending portions 40-0 through 49-9. These radially extending contactformations may be characterized as -units" contacts. The contacts 40-0through 49-9 are arranged to lie on a circle concentric with the annularpattern defined by the tens contacts 40 through 49.

The tens contacts are segmental in shape and are of equal arcuateextent. The units contacts 40-0 through 49-9 are equally spaced fromeach other proceeding counterclockwise as viewed in FIG. 3; however, itwill be noted that the units contacts 40-0 and 49-9 are closely spacedwith respect to each other. These units" contacts may be characterizedas defining nine equal chords of an imaginary circle and one chordsubstantially shorter than any one of such equal chords.

The units contacts are separated by nine segmental contacts 50 through58 of equal arcuate extent. One of these contacts, e.g., the contact 50,acts as a common contact for the units contacts. The annular contact 38acts as a common contact for the tens" contacts 40 through 49.

The hub 14 mounts a movable contact 60, as by means of a pair of pinformations 14a on the former received within suitable apertures on thelatter. This movable contact includes a wiper finger 60a arranged forone-at-a-time wiping or sliding engagement with the tens" contacts 40through 49. This movable contact has another wiper finger 60b arrangedfor continuous sliding engagement with the common contact 38.

Also mounted on the hub 14 for rotation therewith is another movablecontact 62 having ten radially extending, equally spaced, contactfingers 62a through 62j. These contact fingers are arranged for wipingengage ment with the units contacts 40-0 through 49-9 and with thesegmental contacts 50 through 58. The spacing of these contact fingerson the movable contact 62 and the spacing of the units contacts are suchthat only one of the contact fingers 62a through 62] may engage only oneof the units contacts 40-0 through 49-9 at any one time. This spacing issuch that one of the fingers 62a through 62j will always be inengagement with the common contact 50.

It should be mentioned that all of the fixed contact strips on the board26 are preferably formed of copper or other good conducting materialprinted or otherwise formed on such board. The movable contacts 60, 62are also preferably made of copper and move in unison upon rotation ofthe knob 13.

In FIG. 3, the contacts are arranged to define number 93, this resultingbecause the contact wiper 60a is in engagement with the tens contact 49,which represents 90, and because the contact finger 62e is in engagementwith units" contact 43-3, which represents 63.? I

It will be understood that the wiper finger 60a and the contact finger62a lie in a common vertical plane perpendicular to the board 26 andpassing through the center of rotation designated 64. The 100 position,which may also be characterized as a 0 position, is defined when thewiper finger 60a engages the extreme right hand portion (as viewed inFIG. 3) of the tens contact 40 and when the contact finger 62a engagesthe units contact 40-0. The tens contacts 40 through 49 constitute tensfrom 00 to 90, respectively. The units contacts 40-0 through 49.-9constitute units from 0 to 9.

As soon as the movable contacts are rotated in a counterclockwisedirection (as viewed in FIG. 3) from the 100 position as just described,the contact finger 62b will engage the units contact 41-1 simultaneouslywith disengagement of thecontact finger 62a from the units contact 40-0thereby to define the 01 position. On the next increment ofcounterclockwise rotation of the movable contacts, the contact finger620 will engage the units" contact 42-2 simultaneously withdisengagement of contact finger 62b with the units contact 41-1 therebyto define the 02 position.

During the aforedescribed movement of the contact fingers 62a through62c, the wiper 60a will remain in contact with the tens contact 40 whichrepresents 00.However, as the contact finger 62j comes into engagementwith the units contact 40-0, the wiper 60a will simultaneously come intoengagement with the tens contact 41 (representing l0) thereby to definethe 10 positio It shouldnow be apparent that for one complete revolution of the movable contacts 60, 62 with respect to the fixed contactstrips on the board 26, one hundred switching sequences are achieved.The wiper 60a engaging the tens contacts 40 through 49 will establishten contact positions, and during the time each of these contacts iswiped by the finger 60a, i.e., during each 36 of rotation, the contactfingers 62a through 62] will establish ten contact sequences orswitching arrangements. One of the fingers 62a through 62j is always inengagement with the contact 50 which acts as a common units contact; thefinger b is always in engagement with the annular contact 38 which actsas a common tens contact. When the knob 13 is rotated to select anumber, the contacts 60, 62 will thereby be moved to engage the fixedcontacts for establishing the corresponding switching pattern.

Referring to FIG 5, the contact strips 40 through 49 are connected in anetwork of series arranged resistors 65a through 65j. Since the tenscontacts 40 through 49 are integral with the units contacts 40-0 through49-9, one set of resistors serves both the tens" and units" functions.As noted, the movable contact fingers 60a and 62s are in engagement withcontact plates 49 and 43 (portion 43-3) respectively, thereby defininginput selection 93 and corresponding with the disposition of thecontacts as illustrated in FIG. 3.

This resistor network and the movable contacts are connected to theassociatedslide projector by conductors 66a, 66b, 66c and 66d, allcontained within a suitable cable extending between such projector andthe I The contact member 72, which is the units remote control console10. (The lines for the actuate switch in the handpiece are notillustrated in FIG. 5) The random selection circuitry and associatedcontacts within the projector are shown only in block form in FIG. 5 asa tens section 67 and a units section 68.

It should be apparent that for each position of the knob 13 apredetermined electrical resistance will be established by the contactscontrolled thereby and that the resistance for each position will bedifferent from the resistances for all other positions. Reference may behad to the parent application identified above for a completedescription of the random selection circuitry and associated componentswithin the projector which utilize such input information. Briefly, thecircuitry shown in that application operates by what may be termed abalanced resistance principle. According to this principle, when theselector knob on the control console is actuated to select a certainslide space in the tray, the contact members moved during this operationcause a switching function to establish a predetermined electricresistance. Each selection of spaces within the tray results in adifferent resistance value. A network of resistors is contained withinthe slide projector and is associated with fixed and movable contacts toestablish a predetermined electrical resistance for each of thepositions of the tray. To this end, certain contacts 1 move in unisonwith the tray and cooperate with fixed contacts to establish theelectrical resistance for each tray position.

When a selection is made by the remote control handpiece and when theactuate switch is closed, a circuit is completed which energizes a motorin the projector thereby causing rotation of the tray. When the trayrotates such that the resistance of the elements within the projectorequals the resistance established by selection of the desired slide atthe control console, the. projector and remote control resistances arebalanced thereby de-energizing' the motor and stopping the'tray with theselected tray space positioned adjacent the projection gate. Again,reference should be had to my copending application for a detaileddescription of the random selection circuit.

F IG. 6 illustrates another embodiment of the present invention whichmay be used to define the arrangement of fixed and movable contactswithin the slide projector. The contact arrangement illustrated in thisfigure permits the alternate use of a 100 slide tray and an 80 slidetray, all more fully explained in my copend' ing application identifiedabove.

A member (not shown) on the projector and which is driven with the slidetray mounts four contact members 70, 71, 72 and 73 (only fingers 73a,73h are illustrated) for movement therewith. A pair of fasteners (notshown) mounts these various contacts in a sandwich-type relation, thecontacts being electrically insulated from each other by suitabledielectric washers. Contact member 70, which is a tens contact for the80 slide tray," includes contact fingers 70a and 70b. Contact member 71,which is the tens" contact for the 100 slide tray," includes contactfingers 71a and 71b.

contact for the 100 slide tray," includes ten equally spaced contactfingers 72a through 72j. Contact member 73, which is the units" contactfor the 80 slide tray, includes eight equally spaced contact fingers,only fingers 73a and 7311 being shown.

All of the contact fingers just mentioned are in simultaneous wipingengagement with contact strips on a fixedly mounted contact plate 75.This contact plate includes a continuous annular contact strip 76; thisstrip is continuously wiped by the contact finger 7 lb. The plate mountsten contact strips 80 through 89. The outermost portions of the contactstrips 80 through 87 and the two contact strips 88, 89, define tencontact areas, each of identical arcuate extent, which are arranged forone-at-a-time wiping engagement by the contact finger 7 la.

Also mounted on the plate 75 in identical opposite hand relation is apair of arcuate contact strips 90, 92. Each of these strips is alwaysengaged by at least three of the contact fingers 72a through 72j.However, this is not critical, it being only necessary for one of thestrips 90 or 92 to be engaged at all times by any one of these fingers.The contact board 75 mounts a first set of units contacts through 104,and in diametrically opposed relation, a second set of units contactsthrough 109. The innermost portions of the contacts 100 through 109 arearranged to be engaged by the contact fingers 72a through 72j; theoutermost portions of these contacts are arranged to be engaged by thefingers 73a through 73h. The units contacts are arranged according to aVernier principle such that only one of the contacts 100 through 109 maybe engaged at any one time by one of the fingers 720 through 72j or 73athrough 73h. Assuming rotation of the contact member 72 in a clockwisedirection as viewed in FIG. 5, the contacts 100 through 109 are engagedaccording to the following sequence: 100, 105, 101, 106, 102, 107, 103,108, 104, 109.

A pair of identical contact strips 100, ll 1 is mounted on the plate 75adjacent the periphery thereof. Each one of these contact strips isalways engaged by three of the contact fingers 73a through 73h. However,this is not critical as it is only necessary for one of the contacts 110or 111 to be engaged at all times by one of these contact fingers.

It is noted that the contact strips 80 through 87, at the innermostportions thereof, define eight contact segments or areas of equalarcuate extent (except for the inner arcuate portion of strip 80 as willbe explained below); these contact areas may be considered asdefiningtens contacts for establishing 79 positions of the 80 slide tray fornumbers 01 through 79. The inner portion of contact 80 is slightlyshorter than the corresponding portions of contacts 81 through 87; thisinner portion of contact 80 defines positions or numbers 01 through 09.An innermost portion 88a of the contact 88 defines the 80" position ofthe 80 slide tray. These innermost portions of the contact'strips 80through 88 are arranged to be engaged one at a time by the contactfinger 70a. The plate 75 is provided with a continuous annular contactstrip 112 which is continuously wiped by the contact finger 70b.

It should be apparent there are one hundred different contact engagementpositions considering the contact fingers 71a, 72a through 72j and thecontact strips 80 through 89'and 100 through 109. This results since thecontact finger 71a is arranged for one-at-a-time wiping engagement withten of the tens contacts 80 through 89 and since each one of the tencontact fingers 720 through 72j will engage each of the ten units"contacts 100 through 109. It will be understood that each of thesecontact engaging positions establishes a predetermined electricalresistance corresponding to each of the one hundred spaces in the 100slide tray". It will be appreciated that the arcuate spacing between theunits contacts 100 through 109 is 3.6, this being the result of360divided by one hundred, the total number of spaces in the 100 slidetray.

Consideringthe 80 slide tray, the contact finger 70a is arranged forone-at-a-time wiping engagement with the tens contact strips 80 through88. There are eight of the contact fingers 73a through 73h; during acomplete rotation of the contact 73, each of the eight fingers thereofwill engage, in one-at-a-time relation,,

the outermost portions of the contact strips 100 through 109.Thisarrangement of contact strips just described will provide eightydifferent predetermined electrical resistances corresponding to theeighty spaces in the 80 slide tray. Accordingly, the arcuate spacingbetween the outermost portions of the contact strips 100 through 109 is4.5", this being the result of 360 divided by 80. It will be noted thatthe contact strip 89 is not used when the projector is associated withthe 80 slide tray.

Reference should be had to the parent application for a completedescription of the circuitry associated with the arrangement of fixedand movable contacts just described. It is sufficient to state hereinthat when the contact 72 is switched into the circuit, one hundredpredetermined electrical resistances may be established correspondingrespectively to the spaces in a 100 slide tray. When the contact 72 isswitched out and the contact 73 switched in, eighty predeterminedelectrical resistances may be established corresponding respectively tothe spaces in an 80 slide tray.

It should be understood that in lieu of the contact arrangement shown inFIG. 6, a contact arrangement identical to that shown in FIGS. 2 and 3may be incorporated within the slide projector. Also, it will beunderstood by those skilled in the art that the contact arrangementshown in FIG. 6 is suitable for incorporation in a remote controlhandpiece in association with a selector knob and indicia for indicatingthe selected slide space.

The remote input or control console 10 shown and described herein isadapted only for use with a 100 slide tray. However, it will beunderstood that such console may be readily adapted for use with trayshaving other than one hundred slide receiving spaces, such as the 80slide tray mentioned herein. In the case of the 80 slide tray, suitableswitching may be provided to prevent actuation of the circuit when anynumber from 81" through 99" is selected when such tray is in use. Suchswitching is shown and described in my copending application.

I claim:

1. A rotary switching device to set up a separate contact conditionrepresenting each of a plurality of object positions in a transportableobject holder of a randomselection slide projector or the likecomprising:

a. an array of tens contact formations arranged to define an annularpattern and each representing a series of ten object positions;

b. a set of at least ten units contact formations arranged to lie on animaginary circle concentric with said annular pattern, and eachrepresenting an individual object position within each series of tenpositions;

c. first contact means having a first contact finger arranged for one ata time wiping engagement with said tens contact formations;

(1. second contact means having a plurality of second contact fingers,the number of which when multiplied by the number of units contactformations equals the product of ten times the number of tens contactformations, said second contact fingers being arranged such that onlyone thereof engages only one of said units contact formations at any onetime, and also such that each of said contact fingers engages each ofsaid units" contact formations during a switching cycle defined by saidfirst contact finger engaging each of said tens contact formations,

e. means mounting said tens and units" contact formations in a fixedrelationship with respect to each other; and

f. rotatable hub means for mounting said first and second contact meansin a fixed relationship with respect to each other for rotationalmovement relative to said tens and units contact formations, toestablish an individual contact condition for each of said tens andunits contact formations engaged by said first and second contact means,respectivelyv 2. The switching device according to claim 1 wherein saidtens contact formations are equal in number to the number of unitscontact formations and wherein the former are integral with the latter,respectively.

3. The switching device according to-claim 2 further defined by:

a. said second contact means being defined by ten radially extending,equally spaced fingers; the distal ends of which are generally coplanar;

b. said tens".contact formations being defined by segments of a circle,such formations being of equal arcuate extent; and

c. said units contact formations being spaced from each other to definenine equal chords of such imaginary circle and one chord substantiallyshorter than one of said equal chords.

4. The switching device according to claim 1 further defined by: i

a. said second contact means being defined by ten radially extending,equally spaced fingers, the distal ends of which are generally coplanar;and one of b. said units contact formations being tenin number andspaced from each other to define nine equal chords of said imaginarycircle and one chord substantially shorter than one of said equalchords. I Y

5. The switching device according to claim 4 wherein said tens" contactformations are ten in number and are integral with respective unitscontact formations.

6. The switching device according to claim 5 wherein at least one othercontact formation is arranged between two of said units contactformations and has an arcuate extent such that it is always engaged byone of said second contact fingers when any of said units" contactformations is engaged by any one of the other of said second contacts.

7. The switching device according to claim 1 further defined by:

a. circuit means defining a random selection circuit for a slideprojector; and

b. said circuit means including a plurality of resistance elementsarranged in series relationship by respective elements being connectedbetween adjacent ones of said tens contact formations.

8. The switching device according to claim 7 further defined by:

a. said second contact means being defined by ten radially extending,equally spaced fingers, the distal ends of which are generally coplanar;

b. said units contact formations being ten in number and spaced fromeach other to define nine equal chords of said imaginary circle and onechord substantially shorter than-one of said equal chords; and

c. said tens contact formations being ten in number and being integralwith respective units contact formations.

9. A switching device according to claim 1 wherein said second contactfingers of said second contact means are equally spaced, radiallyextending and have distal ends which are generally coplanar.

10. A switching device according to claim 1 wherein said hub meansincludes a disc having a plurality of numerals thereon, eachcorresponding to an object position.

11. A switching device according to claim 10 further comprisingperipheral indexing teeth on said disc; and manually operable indexingpawl means adapted to engage the peripheral indexing teeth to advancethe disc from one numeral to the next.

12. A switching device according to claim 10 wherein said hub meansincludes a knob to permit manual rotation.

13. A switching device according to claim 1 wherein said hub means isdisposed in operative connection with a rotary object holder forrotational movement therewith.

14. A rotary switching device according to claim 1 further includingmeans to set up separate contact conditions representing each of aplurality of object positions in first and second alternatetransportable object holders having different numbers of positions, saidmeans comprising:

a. a second array of tens contact formations different in number fromsaid first stated array of tens contact formations and arranged todefine an annular pattern, wherein each of said second tens" contactformations represents a series of ten object positions in said secondobject holder;

b. a second set of at least ten units contact formations arranged to lieon an imaginary circle concentric with said first stated setof unitscontact formations and spaced from each other a greater distance thenadjacent ones of said first stated set, wherein each of said secondunits" contact formations represents an individual object positionwithin each series of ten object positions represented by each of saidsecond tens contact formations;

0. third contact means having a third contact finger mounted on said hubmeans and arranged for one at a time wiping engagement with said secondarray of tens contact formations; and

d. fourth contact means mounted on said hub in a fixed relationship withsaid third contact means and having a plurality of fourth contactfingers the number of which when multiplied by the number of unitcontact formations in said second set equals the product of ten timesthe number of tens contact formations in said second array, said fourthcontact fingers being arranged such that only one thereof engages onlyone of said second units contact formations at any one time, and alsosuch that each of said fourth contact fingers engages each of saidsecond units contact formation during a second switching cycle definedby said third contact finger engaging each of said second tens contactformations.

15. A switching device according to claim 14, further comprising aplurality of contact plates having first portions which define saidfirst stated array of tens contact formations and second portions whichdefine said second array of tens contact formations.

1. A rotary switching device to set up a separate contact conditionrepresenting each of a plurality of object positions in a transportableobject holder of a random selection slide projector or the likecomprising: a. an array of ''''tens'''' contact formations arranged todefine an annular pattern and each representing a series of ten objectpositions; b. a set of at least ten ''''units'''' contact formationsarranged to lie on an imaginary circle concentric with said annularpattern, and each representing an individual object position within eachseries of ten positions; c. first contact means having a first contactfinger arranged for one at a time wiping engagement with said''''tens'''' contact formations; d. second contact means having aplurality of second contact fingers, the number of which when multipliedby the number of ''''units'''' contact formations equals the product often times the number of ''''tens'''' contact formations, said secondcontact fingers being arranged such that only one thereof engages onlyone of said ''''units'''' contact formations at any one time, and alsosuch that each of said contact fingers engages each of said''''units'''' contact formations during a switching cycle defined bysaid first contact finger engaging each of said ''''tens'''' contactformations; e. means mounting said ''''tens'''' and ''''units''''contact formations in a fixed relationship with respect to each other;and f. rotatable hub means for mounting said first and second contactmeans in a fixed relationship with respect to each other for rotationalmovement relative to said ''''tens'''' and ''''units'''' contactformations, to establish an individual contact condition for each ofsaid ''''tens'''' and ''''units'''' contact formations engaged by saidfirst and second contact means, respectively.
 2. The switching deviceaccording to claim 1 wherein said ''''tens'''' contact formations areequal in number to the number of ''''units'''' contact formations andwherein the former are integral with the latter, respectively.
 3. Theswitching device according to claim 2 further defined by: a. said secondcontact means beIng defined by ten radially extending, equally spacedfingers; the distal ends of which are generally coplanar; b. said''''tens'''' contact formations being defined by segments of a circle,such formations being of equal arcuate extent; and c. said ''''units''''contact formations being spaced from each other to define nine equalchords of such imaginary circle and one chord substantially shorter thanone of said equal chords.
 4. The switching device according to claim 1further defined by: a. said second contact means being defined by tenradially extending, equally spaced fingers, the distal ends of which aregenerally coplanar; and one of b. said ''''units'''' contact formationsbeing ten in number and spaced from each other to define nine equalchords of said imaginary circle and one chord substantially shorter thanone of said equal chords.
 5. The switching device according to claim 4wherein said ''''tens'''' contact formations are ten in number and areintegral with respective ''''units'''' contact formations.
 6. Theswitching device according to claim 5 wherein at least one other contactformation is arranged between two of said ''''units'''' contactformations and has an arcuate extent such that it is always engaged byone of said second contact fingers when any of said ''''units''''contact formations is engaged by any one of the other of said secondcontacts.
 7. The switching device according to claim 1 further definedby: a. circuit means defining a random selection circuit for a slideprojector; and b. said circuit means including a plurality of resistanceelements arranged in series relationship by respective elements beingconnected between adjacent ones of said ''''tens'''' contact formations.8. The switching device according to claim 7 further defined by: a. saidsecond contact means being defined by ten radially extending, equallyspaced fingers, the distal ends of which are generally coplanar; b. said''''units'''' contact formations being ten in number and spaced fromeach other to define nine equal chords of said imaginary circle and onechord substantially shorter than one of said equal chords; and c. said''''tens'''' contact formations being ten in number and being integralwith respective ''''units'''' contact formations.
 9. A switching deviceaccording to claim 1 wherein said second contact fingers of said secondcontact means are equally spaced, radially extending and have distalends which are generally coplanar.
 10. A switching device according toclaim 1 wherein said hub means includes a disc having a plurality ofnumerals thereon, each corresponding to an object position.
 11. Aswitching device according to claim 10 further comprising peripheralindexing teeth on said disc; and manually operable indexing pawl meansadapted to engage the peripheral indexing teeth to advance the disc fromone numeral to the next.
 12. A switching device according to claim 10wherein said hub means includes a knob to permit manual rotation.
 13. Aswitching device according to claim 1 wherein said hub means is disposedin operative connection with a rotary object holder for rotationalmovement therewith.
 14. A rotary switching device according to claim 1further including means to set up separate contact conditionsrepresenting each of a plurality of object positions in first and secondalternate transportable object holders having different numbers ofpositions, said means comprising: a. a second array of ''''tens''''contact formations different in number from said first stated array of''''tens'''' contact formations and arranged to define an annularpattern, wherein each of said second ''''tens'''' contact formationsrepresents a series of ten object positions in said second objectholder; b. a second set of at least ten ''''units'''' contact formationsarranged to lie on an imaginary circle concentric with said first statedset of ''''uNits'''' contact formations and spaced from each other agreater distance then adjacent ones of said first stated set, whereineach of said second ''''units'''' contact formations represents anindividual object position within each series of ten object positionsrepresented by each of said second ''''tens'''' contact formations; c.third contact means having a third contact finger mounted on said hubmeans and arranged for one at a time wiping engagement with said secondarray of ''''tens'''' contact formations; and d. fourth contact meansmounted on said hub in a fixed relationship with said third contactmeans and having a plurality of fourth contact fingers the number ofwhich when multiplied by the number of ''''unit'''' contact formationsin said second set equals the product of ten times the number of''''tens'''' contact formations in said second array, said fourthcontact fingers being arranged such that only one thereof engages onlyone of said second ''''units'''' contact formations at any one time, andalso such that each of said fourth contact fingers engages each of saidsecond ''''units'''' contact formation during a second switching cycledefined by said third contact finger engaging each of said second''''tens'''' contact formations.
 15. A switching device according toclaim 14, further comprising a plurality of contact plates having firstportions which define said first stated array of ''''tens'''' contactformations and second portions which define said second array of''''tens'''' contact formations.